A new analysis of waterfowl monitoring surveys spanning 30 years, representing one of the world’s largest wildlife datasets, has shown for the first time that the vitality of waterfowl hunting in the western United States is linked to the size and health of Baja California lagoon habitats where ducks, geese, and other birds spend their winters.

Published in the Human Dimensions of Wildlife journal, the study led by researchers at Scripps Institution of Oceanography at UC San Diego revealed that one square kilometer of coastal lagoon in Mexico is worth as much as $1,640 in duck-hunting revenue in the U.S. and generates a similar amount in benefits for the hunters themselves.

“The healthier the coastal lagoons in Mexico, in terms of the integrity of their freshwater and mangrove forests, the larger the abundance of waterfowl wintering in these lagoons,” said Nadia Rubio-Cisneros, a Scripps graduate student and lead author of the study. “The number of waterfowl that migrate through the U.S. and Canada depends on their abundance in Mexican coastal lagoons during the winter. In other words, waterfowl hunting in the U.S. critically depends on the health of these Mexican ecosystems.”

Millions of waterfowl migrate annually along the Pacific coast of North America. The U.S., Canada, and Mexico are home to more than 27 species of waterfowl that travel along Pacific and Central migration corridors, or flyways.

Waterfowl wintering in Mexican coastal lagoons depends strongly on the organic matter input from mangroves and the habitat these lagoons provide. Wintering coastal lagoons supply necessary conditions for critical waterfowl life stages such as feeding, courtship, and molting. In spring, the waterfowl fly back to their northern breeding grounds and support recreational hunting and ecotourism in the U.S. and Canada.

Even though the number of hunters in the U.S. has declined slightly in the last few decades, revenue generated from duck hunting licenses and duck stamps remains a critical resource for the conservation of waterfowl populations and habitat in the U.S. Additionally, duck stamp purchases represent only a fraction of other expenditures associated with waterfowl hunting, including travel costs, hunting equipment, and state and federal tax revenues, all of which together generate billions of dollars annually.

The scientists combined surveys on populations, habitat, and harvest collected by the U.S. Fish and Wildlife Service since the 1970s. Using only data from the Pacific Flyway, authors reported that the revenue generated by duck stamp sales in the U.S. is $4.68 million per year. The authors calculated that Mexican wetlands generate additional economic benefits for waterfowl hunters estimated between $3 million and $6 million. These surplus benefits suggest a possible source of funding to conserve habitat beyond the borders of the U.S., the authors say in their study.

“A take-home message of this study is that waterfowl hunting in the U.S. is supported by an ecosystem in Mexico, through nearly one million birds that winter in the eastern side of the Gulf of California,” said Octavio Aburto-Oropeza, a Scripps assistant professor and co-author of the study. “The willingness to pay for stamps by U.S. hunters certainly exceeds that which they actually pay, and this may stimulate plans to establish a payment of ecosystem services (PES) program at a transnational scale.”

The most important result of the paper, the authors say, is finding for the first time that there is a positive correlation between the winter abundance of migratory waterfowl in Mexico, the harvest rates of these birds in the U.S., and the associated duck-stamp sales. Given the results, they argue that under the existing cross-border ecosystem service in North America there may be losses of benefits to birders and waterfowl hunters if habitat size or quality decline.

The paper notes that although the U.S. and Canada have been involved in conservation initiatives for migratory birds since the beginning of the twentieth century, as part of international cooperation agreements between these countries, Mexico joined these conservation actions several decades later. Most importantly, wetlands in Mexico are disappearing at a national rate of seven percent annually because of sedimentation, eutrophication, and deforestation, and are facing increasing pressures to transform these habitats into shrimp farms and tourism developments. In fact, one of the most important Mexican coastal lagoons for the entire Pacific Flyway, Marismas Nacionales in the State of Nayarit, is currently under threat of a decrease in freshwater flows due to the proposed construction of a dam upstream.

“These results highlight the need for more cooperation among the countries of North America, in order to preserve wintering grounds for migratory waterfowl in addition to their summer nesting habitat,” said Exequiel Ezcurra, Director of the University of California Institute for Mexico and the United States (UC MEXUS) and co-author of the article. “After viewing these results, hunters in the U.S. and Canada may be willing to contribute to create this large, long-term program of payment of ecosystem services for coastal lagoons and wetlands in Mexico.”

The scientists assert that these private funds could motivate Mexican government agencies to combine efforts with the U.S. and Canada to establish new mechanisms to protect critical wetlands in western Mexico.

“This study illustrates the vital importance of conserving the Mexican coastal wetlands that serve as critical wintering habitat for migratory water birds in the Pacific Flyway,” said Michael Sutton, vice president of the National Audubon Society. “For years, we’ve focused mainly on protecting nesting habitat for waterfowl in Canada and the United States, while devoting fewer resources to wintering habitat in Mexico. This study shows we need to spend more time and money protecting the wintering grounds as well.”

In addition to Rubio-Cisneros, Aburto-Oropeza, and Ezcurra, co-authors include Jeremy Jackson of Scripps Oceanography; Jason Murray of the Moore School of Business, University of South Carolina; and Charlotte González-Abraham at UC Riverside.

The research was funded by the David and Lucile Packard Foundation, Consejo Nacional de Ciencia y Tecnología (CONACYT), UC Institute for Mexico and the United States (UC MEXUS), the National Geographic Society/Waitt Grants, and the Walton Family Foundation.

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About Scripps OceanographyScripps Institution of Oceanography at the University of California San Diego, is one of the oldest, largest, and most important centers for global science research and education in the world. Now in its second century of discovery, the scientific scope of the institution has grown to include biological, physical, chemical, geological, geophysical, and atmospheric studies of the earth as a system. Hundreds of research programs covering a wide range of scientific areas are under way today on every continent and in every ocean. The institution has a staff of more than 1,400 and annual expenditures of approximately $195 million from federal, state, and private sources. Scripps operates oceanographic research vessels recognized worldwide for their outstanding capabilities. Equipped with innovative instruments for ocean exploration, these ships constitute mobile laboratories and observatories that serve students and researchers from institutions throughout the world. Birch Aquarium at Scripps serves as the interpretive center of the institution and showcases Scripps research and a diverse array of marine life through exhibits and programming for more than 430,000 visitors each year. Learn more at scripps.ucsd.edu and follow us at Facebook, Twitter, and Instagram.

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